Read that people with ADHD respond differently to drugs than most people, things that would make most people more hyper like caffeine have the opposite effect it calms them down and makes them more focused and Ritalin is the same. So it could have the opposite effect than you want

buy some and try some when you've got nothing important on. have some on a friday night when you've got a relatively clear weekend. maybe you'll end up redecorating your flat, maybe you'll have a freakout and know never to try that shit again. don't run the risk of fucking up your exams with the stuff though.